i just did an example-setup on one of my HP EliteBooks ( 2730 p in this case ) installed Server 2008 64 on GPT and obviously stuck in some update-procedures ( but i forgot already that i have been configuring it ) ; On the same ( internal SSD --- GPT formatted -- don't forget that ) which I already booted for about 50 times i just installed Server 2008 ( manually ) into a VHD and used bootsect to write via nt60-Option BootMGR to the virtual-Disk; Normally i do this to avoid manually copying and configuring the locations for the vhd, as Windows Setup ( at least in 7+ Editions ) gets that and refreshes the BCD with the actually installed VHD-Native-Boot-System as top-entry in bcd-boot-mnu.

However, as i restarted after setup has finished i wanted to boot into the system ( W 2008 Server R2 ) and it tried to boot but shows me the typical can-not-acces-disk-content-error ( whatever the code is - dunno right now ) ;

But when i select the originally installed Win 2008 Server ( not R2 ) on the gpt-formatted ssd to boot, it boots right up, though it takes longer than usually. Hmm, i thought, okay maybe something wrong. Look up the BCD-Store at first, to tell if something there hinders the original Server to boot flawlessly and that gives hint what the fuck the prob is with the R2-one.

Well, because i always do that; i started diskpart before and the diskmgmt.msc and i was wondering already, what da f happened ?

Now i have an inaccessible Windows Server 2008 R2 installed into VHD ( multi-partition; mounted \Windows and \Program Files and \Users to logical Partitions --- all ntfs compressed unit=4k basic primary in vhd is offset=32kb and align=4k ; logicals to be later robocopd by cloning uids ) which boots until it tries to access itself natively ( when 'disk'-sub-system loads ) and a bootable ( originally on GPT installed ) Windows Server 2008 which believes it runs from a mbr-disk and shows 2 primary partitions - one for the Windows-System and the HP-UEFI-Partition ( EFI System Partition );

Thing is : I can boot the Windows Server 2008 now via bootmgr from Compatibility-Mode BUT if i wish to use BOOTMGR from EFI it stops loading; In manual selection of EFI-Boot-by-select-from-file the Primary Partition ( originally GPT Primary where Windows Server 2008 is ) is not shown, instead only the HP-UEFI-System-Partition );

So in fact the GPT-Disk is definitive MBR now, whereas the ESP is accessible form both variants AND the BOOTMGR is accessible from both variants ( like in a manually setup Hybrid-MBR with ESP as active boot partition ) BUT Windows Server 2008 only loads when booted via CSM-BIOS;

After that: Install Windows Server 2008 R2 into vhd ( 1primary plus extended containing 3 logicals, though i would say its the same with one primary --- formatted in mbr-mode ) via manually creating/attaching/configuring/formatting vhd before effectively starting the Windows-SetUp.

After that GPT-Disk is MBR-Disk -- Windows-Boot-Partition is gone -- ESP-BOOTMGR is bootable from EFI and CSM but only loads fully via BIOS-Mode and the VHD hangs at disk-sub-system-activation;

CAN SOMEONE REPRODUCE THAT ? ( because i can ... | btw.: i am too lazy to upload xoto|Screenshots first to then embed them here - but if absolutely needed ... )